Aviemore is in a National Park, where planning regulations prohibit developments such as caravan sites. The nearest equivalent is a self-catering log chalet. Check out the links on the right of this page for further information:
http://www.visitaviemore.com/accommodat.html
The link, from that site, to the VisitHighlands site (where you can search for B&Bs) doesn't seem to be working. Instead, go here and choose one of the booking methods at the top right of the page:
http://www.visithighlands.com/aviemore/
Chris